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reservation: add reservation_object_get_excl_rcu()

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In the atomic modesetting path, each driver simply wants to grab a ref
to the exclusive fence from a reservation object to store in the incoming
drm_plane_state, without doing the whole RCU dance.  Since each driver
will need to do this, lets make a helper.

v2: rename to _rcu instead of _unlocked to be more consistent

Signed-off-by: Rob Clark <robdclark@gmail.com>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
This commit is contained in:
Rob Clark 2016-03-31 16:23:51 -04:00
parent feb46f02c3
commit 824815c4cd
1 changed files with 18 additions and 0 deletions
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18
include/linux/reservation.h
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@ -120,6 +120,24 @@ reservation_object_get_excl(struct reservation_object *obj)
reservation_object_held(obj));
}
static inline struct fence *
reservation_object_get_excl_rcu(struct reservation_object *obj)
{
struct fence *fence;
unsigned seq;
retry:
seq = read_seqcount_begin(&obj->seq);
rcu_read_lock();
fence = rcu_dereference(obj->fence_excl);
if (read_seqcount_retry(&obj->seq, seq)) {
rcu_read_unlock();
goto retry;
}
fence = fence_get(fence);
rcu_read_unlock();
return fence;
}
int reservation_object_reserve_shared(struct reservation_object *obj);
void reservation_object_add_shared_fence(struct reservation_object *obj,
struct fence *fence);